I always thought cats were aliens? Isn't there a book called Cats are from Venus; Dogs are from Mars? Or am I getting confuddled? Otherwise, Gnu, most reputable UK garden centres deal in this sort of thing (which I'm told is highly effective and anything with Ultrasonic in its name must be alien technology, right? although maybe not of the feline persuasion...):

Ultrasonic Cat Repellent

Maybe the Wow! Signal was an Ultrasonic Interstellar blast from such a device in a far distant universe where cats are as much a pain in the hooter, or whatever alien orifice in considered the most sensitive, as they are here on earth. There is a Zappa song called Alien Orifice from the 80s - one of his convulted & obtusely complex things. I once knew a Trad. Irish player back then who could play it on the fiddle in jig-time (and a lot of other Zappa tunes). Maybe he was from another planet too? I swore he grew extra fingers during a session...